Natural gas is said to be present in recoverable reserves that surpass those of crude oil in energy equivalent terms, is low in heteroelement content and thus clean in comparison to other fossil fuel resources, and is thus a resource that is anticipated for effective utilization. For utilization of such a natural gas resource, it is effective to convert methane, which is a main component of natural gas, to gasoline, diesel oil, or other liquid fuel to significantly reduce transport costs. As a realistic synthesis method for converting methane to a liquid fuel, the Fischer Tropsch synthesis (hereinafter referred to as “FT synthesis”) with which a synthesis gas (mixed gas of carbon monoxide and hydrogen) produced via a reforming reaction is converted to a liquid hydrocarbon, etc., (the FT synthesis reaction is generally expressed as: nCO+2nH2→(CH2)n+nH2O) is known. In order to improve hydrocarbon productivity, a catalyst of high rate of conversion of carbon monoxide to hydrocarbon is required in FT synthesis, and various catalysts and methods for production thereof have been developed.
As a conventional art, a “catalyst with which active metal species of cobalt metal and a noble metal are carried on a catalyst carrier having silica as a main component” is disclosed in (Patent Literature 1). Also, a method for producing a hydrocarbon-producing catalyst disclosed in (Patent Literature 1) is that in which “a cobalt compound and a noble metal compound are made to be carried on the catalyst carrier by an impregnation method, an incipient wetness method, or a precipitation method.”
A “catalyst including at least one type of element selected from among platinum group elements and rhenium and made of a cobalt-carrying material produced by a sol-gel method” is disclosed in (Patent Literature 2).
A “catalyst with which zirconium and either or both of cobalt and ruthenium are carried on a metal oxide (carrier) and no less than 75% of a total amount of the zirconium, etc., is carried within ⅕ of a radius directed from an outer surface to a center of the catalyst” is disclosed in (Patent Literature 3). Also, in a method for producing catalyst disclosed in (Patent Literature 3) the catalyst is produced by “spray-impregnating a precursor solution of a metal onto a carrier at 50 to 350° C. while stirring the carrier.”